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Theoretical and Actual Acceleration for an Atwood Machine

  1. Oct 30, 2011 #1
    1. The problem statement, all variables and given/known data

    Include free body diagrams and equations solved independently for acceleration and tension. Note: a and T are to be expressed in terms of m1, m2, and g only.
    Trial 1:Mass1= 55g and Mass2= 60g
    Trial 2:Mass1= 55g and Mass2= 65g
    We are doing 2 trials but i need help with the first one. I'm not sure how to figure out the acceleration and theoretical acceleration, should they be coming out the same?


    2. Relevant equations

    A=(m2-m1/m1+m2)g
    Ath=g(m2-m1/m1+m2)
    T=(2m1m2/m1+m2)g

    3. The attempt at a solution

    Trial 1: A=((60-55)/(60+55))*9.8 = (5/115)*9.8 = 0.426m/s/s
    Ath=9.8*((60-55)/(60+55)) = 9.8*(5/115) = 0.4260m/s/s
    T=(2*55*60/55+60)9.8 = (6600/115)*9.8 = 562.43N
     
    Last edited: Oct 30, 2011
  2. jcsd
  3. Oct 30, 2011 #2

    gneill

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    Staff: Mentor

    Hi Pandaluvv2, welcome to Physics Forums.

    Is this assignment accompanying a hands-on lab? If so, the "actual acceleration" would be the value you measure during the experiment, which would subsequently be compared to the theoretical value that you calculate.

    The formulas that you've arrived at appear to be okay but you need to be careful with the units. Your masses are given in grams but should be converted to kilograms for use in the tension formula. The scaling factors happen to cancel out in the acceleration formula so your result turns out to be correct, but you should be using kilograms there too.
     
  4. Oct 30, 2011 #3
    Okay, that makes sense, I forgot we had found acceleration during class, which would have saved me a bunch of time. The only thing I should change is my mass to kilograms then right? So I can use it for the tension?
     
  5. Oct 30, 2011 #4

    gneill

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    Staff: Mentor

    Yup. Work in kilograms.
     
  6. Oct 30, 2011 #5
    Okay, thank you very much for the help!
     
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